In a multicast session, data is transmitted concurrently to a plurality of participants. Typically, a multicast server writes a packet of data out to the network, and the packet is then received by the various participants in the multicast session.
In a reliable multicast, the dropping of a packet is detected and remedied by retransmission of the packet. Since packets are transmitted concurrently to the various participants in the session, if one participant cannot keep up with the same rate of data transfer as the other participant, then the server either takes time to retransmit the packet, or else slows down the rate of transmission for the session to allow the slow participant to keep up. Thus, when one participant in a multicast session is slow, the speed of transmission to the other participants suffers. In effect, the slow participant becomes the “weakest link in the chain.”